First of all you need to consider the compatibility of graphics with older web browsers. For example, a graphic format known as portable network graphics (PNG) is popular among web designers because of its transparency feature. Transparency is not supported in web browsers like Internet Explorer versions 5 and 6 however the popular GIF format is. GIF does not have transparency capabilities but the idea is to display an image using in the older browsers. Professional web designers know how to code custom style sheets (CSS) to send GIF images to older browsers while using PNG when more modern browsers are detected.
Good web graphic design leverages abstractness in images to reduce square effects. Websites in the early days of the internet had their images neatly placed in different sizes of squares. If a designer wanted an image to seem non-square (for instance, a round button) then the square image background had to be the same color as the page background. This method was good for its time but graphic technology has advanced so that images can have transparent backgrounds and be placed as a layer over another image. No longer do the irregular outlines of images have to be sliced out and placed on a background matching that matches the page. One of the ways this is useful is for placing a semi-transparent background over an image and then using a custom style sheet definition to place text over the semi-transparent area. The semi-transparent area helps provide contrast with the text while allowing a background image to show through partially and then fully above the background area.
Fonts should always be simple. Experienced graphic website designers know that fonts used should be those that can be accessed from all web users whether they are on Microsoft or Macintosh platforms. Two simple yet clean fonts are Helvetica and Futura. While a unique font might give a web page an exotic look, it is quite possible that there are machines without them. Web designers also never use fonts that are graphic-based if they are important for search engine recognition.